Field of the Invention
The present invention relates to a piezoelectric vibration module.
Description of the Related Art
Generally, in portable electronic devices, such as a portable phone, an e-book terminal, a game machine, a portable multimedia player (PMP), as non-limiting examples, a vibration function has been utilized for various applications.
In particular, a vibration generating apparatus for generating the vibration has been mainly equipped in the portable electronic device to be used as an alert function that is a soundless receiving signal.
To keep pace with multi-functionalization of the portable electronic device, a demand for a miniaturized, integrated, and multi-functional vibration generating apparatus is being increased.
Further, to meet the recent demand of users to simply use the portable electronic device, a touch type device performing an input by touching the portable electronic device has been generally adopted.
A concept of a currently generally used haptic device widely includes a concept of reflecting intuitive experience of an interface user and diversifying feedback for a touch, in addition to a concept of performing an input through a touch.
The haptic device generally provides vibrations by repeatedly expanding and/or contracting a piezoelectric element by external power applied thereto. In an ultrasonic linear motor described, for example, in Japanese U.M. Laid-Open Publication No. H2-94486, the piezoelectric element may improve moisture proof and durability.
In the ultrasonic linear motor described in the Japanese U.M. Laid-Open Publication No. H2-94486, a circumference of the piezoelectric element is enclosed with a protective material, for example, silicon rubber so as to improve performance and lifespan of the piezoelectric element under the environment that humidity is high or a considerable amount of dust is generated, such that a collision of a plurality of components configuring the ultrasonic linear motor with the piezoelectric element may be prevented beforehand.
However, the whole portion except for a portion of the piezoelectric element generating a vibration force by a translational motion of the ultrasonic linear motor described in the Japanese U.M. Laid-Open Publication No. H2-94486 is enclosed with the protective material, and thus the expansion or contraction deformation rate of the piezoelectric element cannot but remarkably be reduced.
Thus, according to the conventional art, the protective material may rather act as a factor to reduce the vibration force of the piezoelectric element, and therefore other methods for protecting the piezoelectric element from external factors need to be considered.